Bank of America Corp. is being investigated by the Securities and Exchange Commission over whether the lender broke rules designed to safeguard customer accounts, according to the Wall Street Journal. The bank’s Merrill Lynch unit used a variety of large, complex trades and loans over a three-year period to save on funding costs and free up billions of dollars in cash and securities for trading that the firm would otherwise have needed to keep off-limits, the newspaper reported Tuesday, citing people familiar with the inquiry without naming them.